The present invention relates generally to gas turbines for power generation employing closed-circuit cooling paths for flowing a cooling medium, e.g., steam, to cool the hot gas path components and returning the spent cooling medium to a return, for example, a heat recovery steam generator used in a combined-cycle system. More particularly, the present invention relates to a manifold system for supplying the cooling medium to the buckets of the first and second-stage wheels and returning the spent cooling medium from the buckets to a heat recovery generator.
Cooling of hot gas path components, for example, the buckets of a gas turbine, has been proposed in the past and found particularly efficacious in land-based power generating systems. While gas turbines are typically air-cooled, for example, jet engines employ compressor discharge air for cooling the hot gas components, steam cooling in land-based power generating turbines has been proven more efficient in that the losses associated with the use of steam as a coolant are not as great as the losses realized by extracting compressor bleed air for cooling purposes. Also, in combined-cycle operations, steam cooling is particularly advantageous because the heat energy imparted to the steam as it cools the gas turbine components is recovered as useful work in driving the steam turbine in the combined-cycled operation.
In U.S. Pat. No. 5,593,274, of common assignee herewith, there is disclosed a gas turbine having coaxial steam passages for supplying cooling steam to hot gas components of a rotor, for example, the buckets, and returning the spent cooling steam to a return. Various refinements and improvements to that system have since been proposed. For example, in U.S. patent applications Ser. Nos. 09/489,672 and 09/731,982, an advanced steam cooling system is disclosed. In that system, coaxial supply and return pipes are provided in the rotor bore in communication with a plurality of circumferentially spaced, radially extending tubes for communicating supply cooling steam to and spent return cooling steam from adjacent the rim of the rotor, respectively. A plurality of axially extending cooling steam supply passages are provided at circumferentially spaced locations about the rotor rim. Likewise, a plurality of axially extending, circumferentially spaced return passages are located about the rotor rim. Each supply passage communicates cooling medium from a radial supply tube to a circumferentially extending manifold segment located between the second-stage wheel and the first spacer. Supply tubes extend in forward and aft directions from each supply manifold segment for supplying cooling steam to each of the first and second-stage buckets on the first and second-stage wheels. The return manifold segments are located between the first-stage wheel and the first spacer. Each return manifold segment has tubes in communication with the buckets of the first and second-stage wheels for receiving spent cooling steam and returning the spent cooling steam to the return manifold segment for return along the axial passage to a radial tube for delivery to a heat recovery steam generator. It will be appreciated that multiple supply and return tubes are provided and that there is only a small space for providing the manifold segments, tubes and passages necessary to provide an evenly distributed flow at acceptable pressure losses. Accordingly, there is a need to provide manifold segments in the cooling system of such turbines which make economical use of the allotted space, while simultaneously affording uniform flow at low pressure losses.
In accordance with a preferred embodiment of the present invention, there are provided a plurality of circumferentially extending supply manifold segments, each having a configuration for uniformly distributing the flow of the cooling medium to the first and second-stage buckets, while simultaneously making economical use of the space available for the cooling system. Particularly, each supply manifold segment is disposed in the form of an arc for disposition adjacent the rim of the rotor and has a radially inwardly centrally located inlet in communication with the axial supply passage for supplying cooling steam into the manifold segment. The arcuate portion of each supply manifold segment includes a plurality of exit ports for supplying cooling steam via passageways to each of the first and second-stage buckets of the respective first and second turbine wheels. The supply exit ports open through opposite axial faces of the supply manifold segment and an internal guide is provided for uniformly distributing the cooling flow substantially evenly to the exit ports. The supply manifold segments also have a series of circumferentially spaced recesses along their radial outer surfaces, for reasons which will become clear.
The return manifold segments are also circumferentially spaced one from the other about the rim of the rotor. Each return segment includes a central, radially inward outlet port in communication with the axial return passage for returning spent cooling steam from the return manifold segment to the heat recovery steam generator. Each return manifold segment includes a plurality of inlet ports along opposite axial faces for receiving spent cooling steam from the buckets of the first and second-stage wheels. A plurality of guide vanes are disposed along the inside faces of each return manifold segment to guide the returning spent cooling steam from the inlet ports to the outlet port. These guide vanes reduce the whirling effect of the steam which otherwise creates very high pressure losses.
The supply and return manifold segments are preferably located at substantially the same radial locations about the rotor rim. Crossover tubes are provided each manifold segment to enable flow past the other segment. For example, the supply manifold segment includes crossover tubes extending forwardly below the wings of the return manifold segment for connection with the first-stage buckets. Certain of those crossover tubes extend through openings in the return manifold segments. Likewise, each return manifold segment includes a crossover tube which extends in an aft direction for receiving spent cooling steam from the second-stage buckets. The crossover tubes extend through the recesses along the arcuate rim of the supply manifold segments.
Retention systems are provided for retaining each of the supply and return manifold segments against axial, radial and circumferential displacement relative to the rotor. Preferably, the outer rim of each segment includes one or more ribs for engaging in a recess of an overlying flange on the spacer whereby the segments are prevented from displacement in opposite axial directions. The radial inner projections of the supply and return manifold segments engage a flange and a face on the second and first-stage wheels, respectively, to preclude substantial axial movement in the respective aft and forward directions. Additionally, protuberances projecting from the forward and aft faces of the supply and return manifold segments, respectively, bear against the aft and forward surfaces of the spacer to preclude axial displacement of the segments. To preclude substantial circumferential movement of the segments, a projection having flats on opposite sides thereof is provided on the forward and rear faces of the supply and return manifold segments, respectively. These projections engage in linearly extending slots formed in the aft and forward faces of the spacer, the radial extent of these slots exceeding the radial extent of the projections. Thus, the manifold segments are enabled for radial displacement which is necessary for field assembly and disassembly, while the segments are simultaneously maintained against circumferential displacement about the rotor.
In a preferred embodiment according to the present invention, there is provided a turbine rotor having axially spaced wheels mounting buckets and a spacer between the wheels, a cooling system for cooling the buckets, comprising a plurality of manifold segments circumferentially spaced from one another about and adjacent the rim of the rotor, each manifold segment lying in communication with at least one passage for flowing a cooling medium to or from the manifold segment, each manifold segment having a plurality of ports in communication with flow passageways of turbine buckets of at least one of the turbine wheels, a retention system carried by the manifold segments and cooperable with the spacer for securing the manifold segments to the spacer against substantial axial movement relative to the rotor including a flange on the spacer having one of a generally radially projecting rib and a recess and another of the rib and the recess on each manifold segment, the rib being engageable in the recess to retain the manifold segment on the spacer against substantial axial movement.
In a further preferred embodiment according to the present invention, there is provided a turbine rotor having axially spaced wheels mounting buckets and a spacer between said wheels, a cooling system for cooling the buckets, comprising a plurality of manifold segments circumferentially spaced from one another about and adjacent the rim of the rotor, each manifold segment lying in communication with at least one passage for flowing a cooling medium to or from the manifold segment, each manifold segment having a plurality of ports in communication with flow passageways of turbine buckets of at least one of the turbine wheels, a retention system carried by the manifold segments and cooperable with the spacer for securing the manifold segments to the spacer against substantial movement in a circumferential direction relative to the rotor including slots on one of the spacer and the manifold segments and stops on another of the spacer and the manifold segments engageable with walls of the slots to preclude substantial movement of the manifold segments in a circumferential direction relative to the rotor.
In a further preferred embodiment according to the present invention, there is provided a turbine rotor having axially spaced wheels mounting buckets and spacers between said wheels, a cooling system for cooling the buckets, comprising a plurality of cooling medium supply passages circumferentially spaced from one another about and adjacent a rim of the rotor, a plurality of spent cooling medium return passages circumferentially spaced from one another about and adjacent the rim of the rotor, a plurality of supply manifold segments circumferentially spaced from one another about and adjacent the rim of the rotor, each supply manifold segment lying in communication with at least one of the supply passages for receiving the cooling medium from one supply passage, each supply manifold segment having a plurality of exit ports connecting the supply manifold segment and cooling medium inlets for the turbine buckets of selected axially spaced wheels, a plurality of return manifold segments circumferentially spaced from one another about and adjacent a rim of the rotor, each return manifold segment lying in communication with at least one of the return passages for flowing spent cooling medium from the return manifold segment to the one return passage, each return manifold segment having a plurality of inlet ports connecting the return manifold segment and spent cooling medium outlets for the turbine buckets of selected axially spaced wheels and at least one guide vane within each plurality of supply manifold segments for substantially uniformly distributing the cooling medium to the exit ports.
In a further preferred embodiment according to the present invention, there is provided a turbine rotor having axially spaced wheels mounting buckets and spacers between said wheels, a cooling system for cooling the buckets, comprising a plurality of cooling medium supply passages circumferentially spaced from one another about and adjacent a rim of the rotor, a plurality of spent cooling medium return passages circumferentially spaced from one another about and adjacent the rim of the rotor, a plurality of supply manifold segments circumferentially spaced from one another about and adjacent the rim of the rotor, each supply manifold segment lying in communication with at least one of the supply passages for receiving the cooling medium from one supply passage, each supply manifold segment having a plurality of exit ports connecting the supply manifold segment and cooling medium inlets for the turbine buckets of selected axially spaced wheels, a plurality of return manifold segments circumferentially spaced from one another about and adjacent a rim of the rotor, each return manifold segment lying in communication with at least one of the return passages for flowing spent cooling medium from the return manifold segment to the return passage, each return manifold segment having a plurality of inlet ports connecting the return manifold segment and spent cooling medium outlets for the turbine buckets of selected axially spaced wheels and a plurality of guide vanes within each of the plurality of return manifold segments for guiding the spent cooling medium received from the plurality of inlet ports to the return passage to eliminate pressure losses within the return manifold.